1. Field of the Invention
The present invention relates to a cathode ray tube having a deflection yoke including a circular ferrite core and a deflection coil whose cross-section is in a rectangular shape for improving a deflection sensitivity of the cathode-ray tube, and more particularly to a cathode ray tube, in which one part of a vertical deflection coil having a rectangular shaped cross-section to improve a lead-in capability when winding the vertical deflection coil located between a ferrite core and the holder is separated by a predetermined gap from a holder that isolates a horizontal deflection coil and the vertical deflection coil
2. Background of the Related Art
FIG. 1 is a diagram illustrating a conventional cathode ray tube.
Referring to FIG. 1, the conventional cathode ray tube includes an electron gun 4 for emitting three electron beams, a fluorescent screen 1 on which a fluorescent substance is formed for colliding with the electron beams to generate lights, a shadow mask 2 for performing dichroic operations of the three electron beams, and a deflection yoke 3 for allowing the electron beams to be deflected at predetermined locations on the fluorescent screen 1.
In particular, the deflection yoke 3 includes a horizontal deflection coil 31 for deflecting the electron beam emitted from the electron gun 4 installed in the cathode ray tube in the horizontal direction, a vertical deflection coil 33 for deflecting the electron beam in the vertical direction, a conic shaped ferrite core 34 for improving a magnetic efficiency by minimizing the loss of a magnetic force being generated from the horizontal deflection coil 31 and vertical deflection coil 33, and a holder 32 for fixing the vertical deflection coil 33, the horizontal deflection coil 31 and the ferrite core 34 at predetermined locations and isolating the horizontal deflection coil 31 and the vertical deflection coil 33.
In addition, in a neck part of the deflection yoke 3 are formed a convergence yoke 35 for compensating a misconvergence due to an error of the manufacture process of the deflection yoke and the cathode ray tube, and a pair of ring-shape permanent magnets 36.
FIG. 2 is a diagram illustrating an assembly process of the conventional cathode ray tube.
To give a brief description on the cathode ray tube with reference to FIG. 2, the horizontal deflection coil is installed in the inner part of the holder 32, and the vertical deflection coil 33 is installed in the outer part of the holder 32.
Then, the ferrite core 34 is provided in a manner to wind around the outer surface of the vertical deflection coil 33.
The conventional deflection yoke 3 allows a current having at least 15.75 kHz frequency to flow to the horizontal deflection coil 31 and deflects the electron beam in the cathode ray tube in the horizontal direction using a magnetic field generated by the current.
Also, the deflection yoke 3 allows a current having a 60 Hz frequency to flow to the vertical deflection coil 33 and deflects the electron beam in the vertical direction using a magnetic field generated by the current.
A self-convergence type deflection yoke 3 for allowing three electron beams to compensate for a convergence on a screen without using separate additional circuit and additional device by using a nonuniform magnetic field generated by the horizontal deflection coil 30 and vertical deflection coil 33, has been developing.
That is, by controlling a winding distribution of the horizontal deflection coil 31 and vertical deflection coil 33 and forming a barrel type or pin-cushion type magnetic field in respective regions (opening region, intermediate region and neck region), it is possible to have different deflection forces corresponding to locations of the three electron beams affect the electron beams, and therefore the electron beams converge on the same point though the respective electron beams have respective distances from beginning points to arrival points.
Also, in the case that a magnetic field is formed by flowing a current to the horizontal deflection coil 31 and the vertical deflection coil 33, the magnetic field generated by the horizontal deflection coil 31 and the vertical deflection coil 33 is not strong enough to deflect the electron beams to the whole surface of the screen. Hence the ferrite core 34 having a high magnetic permeability is used to minimize a loss on a feedback path of the magnetic field, thereby improving an efficiency of the magnetic field and increasing a magnetic force. FIG. 3a is a cross-sectional view of a conventional deflection yoke including a deflection coil, whose cross-section being in a rectangular shape, and a rectangular shaped ferrite core. FIG. 3b shows a deflection coil having a rectangular shaped cross-section and a circular ferrite core.
Referring to FIGS. 3a and 3b, when three electron beams pass through a magnetic field area, according to Fleming""s left hand rule, a force applied to each of the three electron beams is deflected, being inversely proportional to the cube of the distance between the inner surface of the deflection coil and the electron beam. As shown in FIG. 3a, because the deflection yoke including the deflection coil 33 and ferrite core 34 having the rectangular shapes respectively is closer to the electron beams than the deflection yoke having the circular deflection coil and the ferrite core, a deflection sensitivity can be improved.
Accordingly, in the case of the deflection yoke including the horizontal deflection coil and vertical deflection coil whose cross-sections are in rectangular shapes, the distance between the electron beam and the deflection coil is shorter by 20% than the conventional deflection yoke including the deflection coil whose cross-section is the circular shape. As a result, horizontal and vertical deflection sensitivities are greatly improved by 20-30%.
Also, given that the deflection coil 33 whose cross-section is the rectangular shape and the inexpensive circular ferrite core 34 as shown in FIG. 3b are used, it is now possible to improve the deflection sensitivity and obtain enhanced cost reduction efficiency.
FIG. 4 shows a state how a conventional horizontal deflection coil whose cross section is a rectangular shape is wounded, and FIG. 5 shows a state how a conventional vertical deflection coil whose cross-section is the rectangular shape is wounded.
Referring to FIGS. 4 and 5, the horizontal deflection coil 31 and the vertical deflection coil 33 are leaded-in and formed in a space between an upper former 20 and a lower former 21. Because the horizontal deflection coil 31, as shown in FIG. 4, is wound on the farther side of a former center line 40, that is, beneath a diagonal line 41, a distance which the horizontal deflection coil 31 must be leaded in from an entrance is short.
However, a relatively large number of vertical deflection coils 33, as shown in FIG. 5, are located closer to the former center line 40, that is, beneath the diagonal line 41 due to the deflection yoke property.
Accordingly, because the vertical deflection coil 33 must be leaded-in from the entrance toward the former center line 40, the vertical deflection coil 33 is subjected to a great frictional force over the long distance in the course of winding.
Also, because the former surface of the vertical deflection coil 33 whose cross-section is the rectangular shape is bended almost perpendicularly in the vicinity of the diagonal line 41, the frictional force becomes greater between the vertical deflection coil 33 and the former surface than a vertical deflection coil with a circular cross-section and the circular former surface.
Therefore, a problem arises in that the vertical deflection coil 33 whose cross-section is the rectangular shape has a poor lead-in capability upon winding.
FIG. 6 shows a cross-sectional diagram of a deflection yoke in a cathode ray tube having a screen ratio of 16:9.
As shown in FIG. 6, in case that the screen ratio is 16:9 not 4:3, the horizontal direction length of a vertical deflection coil 33 is longer than that of a vertical deflection coil of a cathode ray tube having a screen ratio of 4:3. As such, a lead-in capability of the vertical deflection coil 33 becomes worse.
An object of the invention is to solve the above problems and/or disadvantages of the prior art.
Accordingly, one object of the present invention is to provide a deflection coil whose cross-section is a rectangular shape for improving a deflection sensitivity, thereby enhancing a productivity of the deflection coil as well as facilitating a manufacture of the deflection coil.
The present invention relates to a cathode ray tube having a deflection yoke including a circular ferrite core and a deflection coil whose cross-section is a rectangular shape for improving a deflection sensitivity of the cathode-ray tube, and more particularly to a cathode ray tube, in which one part of a vertical deflection coil whose cross-section is a rectangular shape is separated by a predetermined gap from a holder, for improving a lead-in capability when the vertical deflection coil is wound, wherein the vertical deflection coil is located between a ferrite core and the holder for isolating a horizontal deflection coil and the vertical deflection coil.
The cathode ray tube according to the present invention has a deflection yoke including a horizontal deflection coil for deflecting an electron beam being emitted from an electron gun in a horizontal direction, a vertical deflection coil for deflecting the electron beam in a vertical direction, a ferrite core for preventing a loss of a magnetic force generated from the horizontal deflection coil and vertical deflection coil and improving a magnetic efficiency, and a holder for fixing the horizontal deflection coil, the vertical deflection coil and the ferrite core at predetermined locations and isolating between the horizontal deflection coil and the vertical deflection coil, wherein each cross-section of the horizontal deflection coil and the vertical deflection coil has a rectangular shape and a cross-section of the ferrite core has a circular shape, and in the case that an distance from an outer part of the holder to an inner surface of the ferrite core on a vertical axis of a cross-section of the deflection yoke taken along a plane parallel to a panel from an opening end of the ferrite core, is defined as Y, an distance from the outer part of the holder to the inner surface of the vertical deflection coil on the vertical axis is defined as X, and a thickness of the vertical deflection coil 33 on the vertical axis is defined as Z, the distance X from the outer part of the holder to the inner surface of the vertical deflection coil on the vertical axis satisfies a relationship of 0 less than X less than Yxe2x88x92Z.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.